Induction furnace



June 7, 1932.

w/r/vsasss P. H. BRACE INDUCTION FURNACE Filed Jan. 6, 1931 INVENTOR For/er' fig/ace.

ATI'ORNEY electric induction Patented June 7, 1932 PORTER H. BRACE,

OF FOREST HILLS, WILKINSBURG, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF YENNSYLVANIA mnuc'rron ruan'ncn Application filed January 6, 1931. Serial No. 506,920.

My invention relates to electric furnaces and particularly to induction furnaces of relatively large size.

An object of my invention is to provide an furnace of the surroundedpool type and of relatively large size and simple construction.

Another object of my invention is to provide an electric induction furnace having provision for utilizing polyphase electric energy,

Another object of my invention is to provide an electric-induction-furnace assembly embodying a metal-holding chamber of relatively large capacity and one or more metal- 5 melting chambers of relatively small capacity.

Another object of my invention is to provide a furnace structure having a metal-holding chamber provided with a heat-insulating lining of relatively large thickness and one or more metal-melting chambers having a heat-insulating lining of relatively small thickness.

Another object of my invention is to provide an induction furnace embodying means for varying the amount of stirring at the surface of the molten metal.

Another object of my invention is to provide a furnace in which the inductor elements, I

including an energizing coil and a metal melting chamber, shall be so assembled as to be easily and quickly detachable from the rest of the furnace structure without emptying the metal from the metal-holding chamber.

In practicing my invention, I provide a metal-holding chamber, having suitablerefractory heat-insulating walls therearound and a housing for the refractory walls, of relatively large holding capacity and provided with means for tilting or turning the same. When a plurality of metal-melting chambers of relatively small size and capacity are secured to the housing of the metal-holding portion, resilient securing means are provided to connect the two portions. Energizing coils permit of compressing the granular material therein to assist the lining of the chamber in withstanding the relatively high pressure to which it may be subjected.

In the single sheet of drawing:

Figure 1 is a view, partially in horizontal section and partially in side elevation, of an electric induction furnace embodying my invention,

Fig. 2 is an enlarged view, in lateral, vertical section therethrough, taken on the line II II of Fig. 1, and

Figs. 3, 4 and 5 are schematic views showing the furnace structure in diiferent operatmg positions.

Some of the elements which enter into the design and operation of relatively large induction furnaces are the choice of frequency and the question of single-phase or polyphase supply of energy. In the case of relatively small induction furnaces, particularly those of the so-called surrounded-pool type, that is, the type in which an energizing coil of substantially helical shape is located around a bath of metal, it is possible to use frequencies which may be considered high or, at least, to use a frequency which can be generated by an alternating-current generator of substantially standard type.

As the size or capacity of a furnace of this kind increases, the optimum frequency decreases until, in very large furnaces, the optimum frequency may be but-a few cycles per second, this requiring special and expensive generating equipment.

The problem of the refractory lining in large furnaces becomes extremely important, particularly so if it is to be located between the energizing coil and the material being melted. It is obvious that the thicker the lining, the less is the so-called coupling between the energizing coil and the secondary thereof, constituted by the metal to be melted. Both the power factor and the efiiciency of a furnace of this kind having a relatively thick I relatively large power input into the metal being melted, particularly when using highpower input per unit volume, the stirring action on the metal may become excessive and retfileire special means for its control.

ferring to the drawing, I have illustrated-an .electric induction furnace 11 including a metal housin relatively high tem rature. The chamber 16 constitutes a meta -holding or a metal-containing chamber.

Means for tiltin the furnace may be constituted by hearing rackets 17 and 18 engaging stub shafts 19 and 21. A gear wheel 22 may be located on shaft 21 and be rigidly secured thereto to en go a pinion 23 whic is mounted on a crani shaft 24 to permit of eflecting a turning movement of the housing 11. It is, of course obvious that, when housing 11 is made of, ver large metalholding capacity, some other esign than that shown 111 't e drawing for tilting the furnace can be provided, but I have shown the pinion, its operating crank shaft and the cooperating gear' wheel as illustrative of such tilting mechanism.

An opening 26 is provided in the housing 11 which may be utilized not only as the charging door but also as a pouring spout.

A- plurality of relatively small metalmelt' chambers 27 are provided in close operative engagement and connected with the metal-holding chamber 16, the metal-meltin chambers bem located entirely outside 0 the contour o the metal-holding chamber. Each metal-melting chamber 27 is located within a housing 28 which may be made of a suitable high-resistance metal, that is, a metal which will have a tendency to cut down or reduce the temperature rise thereof when it is subjected to an alternatin -current flux. Each chamber 27 is defined y a lining 29 which may be in the form of a crucible of a suitable refractory material, usually employed in'metal melting, or it may be a rammed-in lining.

An energizin coil 31 is located around the crucible 29 an may be of any suitable or desired construction but is here shown as including an inner solid current-conducting portion and an outer tubular current and cooling-fluid conducting portion.v I have shown onl one terminal 32 but it is to be understoo that a second terminal will be provided, in a manner well known in the art.

The crucible or lining 29 may be located on I sulating and heat-insulating material 36 provided between the turns of the energizing coil and between the coil and a set of laminatrons 37 of substantially L-shape. I have illustrated the ma netic laminations 37 generally only and order to increase the ower factor and the efliciency of the energizing coil, although they are not absolutely necessary and may be dispensed with.

The open end portion of housing 28 is of such shape that it may cooperate with the external peripheral surface of housing or casing 12 to effect close interfitting enga ement between the refractory wall 13 and 51e granular refractory material 36in order to I provide a fluid-tight joint. The lining 13 is provided with a plurality of symmetrically spaced openings 38 with which the upper ends of chambers 27 will register when the prefer to employ these in metal-melting. chamber assemblies 27 are in proper operative positions. An annular member 39 is secured, in any suitable or desired manner, to the metal of the housing 12, and its inner peripheral surface may constitute a guide or the outer peripheral surface of an end portion of housing 28.

Resilient means, including a plurality of pivot bolts 41 mounted in recesses in annular member 39, extend through recessesxin an annular member 42 secured to housin 28 intermediate its ends. Nuts 43 and sprm s 44 cooperate with the pivotally mounted olts 41 and the ring 42 to resiliently clamp each metal-melting-chamber assembly in close operative engagement with the main housing.

Compression means is provided to follow up' any possible shrinkage in the granular refractory material 26 and may include a member 46'of cylindrical sha a piston 47 movable therein and adjustab e, as by a hand wheel 48 having screw-threaded engagement with a clamping member 49 of substantially C-shape. Tubular member 46 is bolted against housing 28 which has an opening therein, as shown in Fig. 2 of the drawing.

As was hereinbefore stated, the device embod ing my invention is particularly applicab e, to electric induction furnaces of relatively large capacity in which it is desirable that the heat lost b the molten metal shall be as small as possi 1e and, for this purpose, the thickness of lining 13 is made relatively large, as no melting per se is done in the metal-holding chamber. 'The metal-melting- Ill chamber assembly is relatively small in cam the chamber 27 and flowing upwardly in the central portion thereof, as is'indicated by the broken line arrows in Fig. 2. As the amount of energy transferred from the coil to the metal is increased, this movement of the metal fl, increases and may become very violent, and 7 one of the disadvantages or harmful results of excessive agitation of the surface of the metal is that oxidation of the metal may occur to too great an extent. This may particu- -larly be the case where a single furnace is utilized at different times in the melting of entirely different metals or alloys.

Referring, for instance, to Fig. 2 of the drawing, I have there illustrated a position of the furnace assembly in which the greatest hydrostatic head or ressure on chamber 27 will be provided. If? now, it appears desirable to increase the agitation, the furnace may be tilted to a position substantially such as is shown in Fig. 4 of the drawing where the auxiliary or metal-melting chambers are no longer immediately below the metal-holding chamber but are intermediate a vertical downward and a lateral position relatively thereto. 7

It is, therefore, obvious that, if the furnace assembly is maintained in the position shown in Fig. 3 of the drawing, it' will be possible to transfer a relatively large amount of energy per unit of volume of the molten metal without excessive agitation of the surface of the metal.

In case of damage to one of the metal-melt ing-chamber structures, it becomes necessary to remove the same and replace it by an undamaged unit in the shortest possible time, and, in order to effect this removal and replacement, the furnace structure may be tilted to the .position shown in Fig. of the-drawing, that is, to such an extent that the level of the molten metal will be below the lower edge of the openings 38 so that a housing 28 and the other elements located therein may be removed by temporarily supporting the housing by a chain and a crane, removing the nuts 43 and loosening them to an extent sufficient to permit of, swinging the bolts 41 out of the recesses in ring 42. The replacement of an undamaged unit may be effected in the reverse manner, and it is obvious that such removal and replacement may be effected in a minimum length of time.

Attention may also be called to the fact that the metal-melting-chamber assembly is relatively small and may, therefore, be handled easily and that any damage to a part i thereof will not be as serious to the continued operation of the furnace as would be the case if a single energizing coil extendin around the furnace structure were employe is, in case of damage to one energizing coil, if no metal were leaking, it would be possible to continue energizing two out of three That phases to complete the melting or the refining operation, if this became necessar While I have illustrated and descri (l a furnace embodying a tubular structure, I do not desire to be limited thereto, nor do I desire to be limited to the aligned spaced location of the metal-melting chambers. It is obvious that-the inventive idea of a relatively large-capacity holding chamber and a plurality of melting chambers of relatively small capacity may be applied to other forms of furnaces, among which may be mentioned a furnace of substantially spherical shape.

Referrlng again to the matter of varying the degree of agitation of the metal in the metal-holdingchamber, it may be noted that it is possible to continue supplying energy to the respective energizing coils during the tilting movement or during the time that the furnace is maintained in a tilted position, as shown in Fig. 4 of the drawing.

The device embodying my invention thus provides a relatively simple and highly efficient furnace structure in which the molten metal is protected against excessive heat loss therefrom by a relatively thick heat-insulating lining, and in which the transfer of energy from an energizing coilto metal located entirely therewithin is effected at relatively high efficiency by reason of a high coupling factor therebetween. It is possible, in a furnace embodying my invention, to operate it from a polyphase source of supply of electric energy with little or no electrical unbalance. The inductor element, including the lining surrounding the melting chamber, the energized coil and the housing surrounding these parts may be easily and quickly removed and replaced without the necessity of emptying the metal out of the furnace. As the amount of metal in the melting chamber is relatively small, the thermal losses through the walls surrounding the melting chambers are small, so that a relatively high electrical efficiency is obtained. The vigorous stirring, action in the metal in the melting chambers efiectively prevents localized high temperatures, such as are frequently found in large-capacity furnaces.

The use of relatively small-capacity melting or inductor elements permits of operating a relatively large-capacity furnace at frequencies which are well within the range of those which may be generated by ordinary generating equipment.

Since various modifications may be made in the device illustrated and described with,-

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out departing from the spirit and scope of my invention, I desire that only such limitations shallbe placed thereon as are imposed by the prior art or are set forth in the appended claims.

I claim as my invention:

1. An electric induction furnace including a material-holding chamber of relatively large capacit a pot-type material-melting chamber of relatively small capacity connected thereto and an inductive energizingcoil surrounding said material-melting chamber. 1

2. An electric induction furnace having a" metal-holding-chamber structure of relatively large capacity, a metal-melting-chamber assembl of relatively small capacity and means or resiliently clamping the meltingchamber assembly to the ho ding-chamber structure. I

3. An electric induction-furnace assembly including a metal-holding chamber, a pottype metal-melting chamber projecting from, and communicating with, the metal-holding chamber, said chambers havin refractory walls, an energizin coil locate around the wall of the --meta -melting chamber, and means for varying the degree of surface dis- {:rbance of metal in the metal-holding chamr. 1 4. An electric ino'uction-furnace'assembly including a housing for a metal-holding chamber having an o ning therein, an annular member on sai I housing around said 0 ning, and a housing for a metal-meltin c amber having a portion interfitt' wit the annular member to provide a flfid-tight joint.

5. An electric induction-furnace assembly including a housing for. a metal-holding chamber having an o ning therein, an annular member on sai housing around said opening, a housing for a metal-melting chamber having a portion interfitting with the annular member to provide a fluid-tightjoint, and resilient means for holding the housing of the metal-melting chamber in roper o erative position against the housing of t e metal-holding chamber.

6. An electric induction-furnace assembly including a chamber, a refractory lining therein, an energizing coil around the lining for heating metal located withinthe lining bg inductive action, a housing enclosing the mber, the refractory lining and the energizing coil, granular refractory material in said housing and around said lining and adjustable means for applying pressure to the ranular refractory'material to support the ining against relatively high internal press sures thereagainst. I

7. An electric induction-furnace assembly including a main and an auxiliary housing enclosin a metal-holding chamber and a communicating metal-meltin chamber, granular refractory material in the auxil- 1,aoa,aoa A and around said metal-melting chamber an ad'ustable means for efiecting pressure on sai granular. refractory material to counteract the metal premure. in the metal-meltin chamber.

8. A polyp ase electric induction furnace. includin a casing for a metal-holding chamber of re ativel large capacity, a plurality of relative! sma casings for inductor chambers, an means for removably and resiliently securing said inductor-chamber c against the casing of the metal-holding chamiary housingl 9. A polyphase electric induction furnace including a casin for a metal-holding chamber, a plurality o casings for metal-mel chambers located in symmetrically-spa relation to the vertical axis of the casing of the metal-holding chamber, and means for detachably and resiliently securing the casings of the-metal-meltin chambers against the casing of the metal-ho din chamber.

10. A polyphase electric in uction furnace including a casing for a metal-holding chamber, a plurality of casings for metal-meltin chambers located in symmetrically-spaced relation to the vertical axis of the casing of the metal-holding chamber, and means for detachably and resiliently securing the casings of the metal-melting chambers in interfitting en agement with the casing of the metal-hol ing chamb'er.

In testimony whereof, I'have hereunto subscribed my name this 27th day of December,

PORTER H. BBACE. 

